This keypad telephone encoder circuit was found in ancient American documentation. The components used are common and are not difficult to obtain.
This circuit is based on the LT1004, LT1167, LT307 or LT1490 from Analog Devices. The circuit was...
This circuit, indicated by Texas Instruments, uses a high voltage regulator and a Darlington also...
This circuit is suggested by Texas Instruments and can be used on an assembly line to drive an...